The present invention relates to novel methods and compositions for the treatment of primary and metastatic cancers. These methods and compositions utilize catechins, including but not limited to, epigallocatechin gallate (EGCg), epicatechin (EC), epicatechin gallate (ECG), and epigallocatechin (EGC), which are found in varying levels in tea leaves. The unique compositions of the invention contain various amounts of the catechins, including combinations of catechins, or catechins and other therapeutic agents. These compositions are particularly useful for the treatment of primary and metastatic cancers in humans. The invention also encompasses the varying modes of administration of the therapeutic compounds or compositions.
Tea is generally in the form of black, oolong, and green tea, all originating from the tea plant, Camellia sinensis. Tea is cultivated in approximately thirty countries worldwide, and is consumed globally. Although the level of tea consumption varies around the world, it is believed that tea consumption is second only to water (Ahmad et al., 1998, Nutrition and Chemical Toxicity, John Wiley and Sons, Sussex, England, pp. 301-343). Black tea is consumed predominantly in Western and some Asian countries and green tea is consumed predominantly in China, Japan, India, and a few countries in North Africa and the Middle East (Ahmad et al., 1998, Nutrition and Chemical Toxicity, John Wiley and Sons, Sussex, England, pp. 301-343).
Green tea has been prized as a traditional tonic and has been widely consumed in East Asia. Recent studies have attempted to link green tea to antioxidant benefits including protection against the damage caused by cigarette smoke, pollution, stress, and other toxins (for an overview, see e.g., Mitscher, 1998, The Green Tea Book, Avery Publishing Group, Garden City Park, New York and Weisburger, 1997, Can. Lett. 114:315-317).
An empirical link between green tea and its cancer prevention properties was made in the late 1980s (Khan et al., 1988, Can. Lett. 42:7-12 and Wang et al., 1989, Carcinogenesis 10:411-415). Epidemiological studies show that cancer onset of patients in Japan who had consumed ten cups of green tea per day was 8.7 years later among females and 3 years later among males, compared with patients who had consumed under three cups per day (Fujiki et al., 1998, Mutation Res. 402:307-310). As such, a possible relationship between high consumption of green tea and low incidence of prostate and breast cancer in Asian countries where green tea consumption is high has been postulated (Liao et al., 1995, Can. Lett. 96:239-243 and Stoner and Mukhtar, 1995, J. Cell. Biochem. 22:169-180). However, because of the many variables in lifestyle inherent to such a study, a definitive link between green tea and its cancer prevention effects could not be concluded.
Scientists have now identified many of the natural substances in green tea that may provide the majority of its health benefits. One class of chemicals that has attracted much study is the polyphenols, also known as catechins.
The polyphenols describe a class of substituted phenolic compounds that are known as flavanols or catechins. The polyphenols in green tea that have been identified are catechin (C), epicatechin (EC), gallocatechin (GC), gallocatechin gallate (GCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCg) (FIG. 1). In addition, caffeine, theobromine, theophylline, and phenolic acids, such as gallic acid, are also present as constituents of green tea in smaller quantities than the polyphenols (Ahmad et al., 1998, Nutrition and Chemical Toxicity, John Wiley and Sons, Sussex, England, pp. 301-343).
Epigallocatechin gallate (EGCg), the major catechin in green tea, has been the focus of many studies to determine if it is responsible for the antioxidant and anti-carcinogenic effects of green tea, as reviewed by Ahmad and Mukhtar, 1999, Nutr. Rev. 57:78-83. The administration of a pharmacologically effective amount of EGCg has been alleged to reduce the incidence of lung cancer in a mammal (U.S. Pat. No. 5,391,568). A bioavailability study showed that frequent green tea consumption results in high levels of EGCg in various body organs, suggesting that green tea consumption may protect against cancers localized to different sites of the body (Sugunama et al., 1998, Carcinogenesis 19:1771-1776).
EGCg has been implicated in blocking DNA transcription of a number of genes in cancer cell lines. For example, in the human epidermal carcinoma cell line A431, EGCg inhibits the DNA and protein synthesis of the growth factor receptors epidermal growth factor receptor (EGF-R), platelet-derived growth factor receptor (PDGF-R), and fibroblast growth factor receptor (FGF-R) (Liang et al., 1997, J. Cell. Biochem. 67:55-65). EGCg has also been implicated in blocking transcription of nitric oxide (NO) synthase by inhibiting the binding of transcription factor NFxcexaB to the NO synthase promotor (Lin and Lin, 1997, Mol. Pharmacol. 52:465-472 and Chan et al., 1997, Biochem. Pharmacol. 54:1281-1286). In the tumor cell line JB6, EGCg inhibits AP-1 transcriptional activity (Dong et al., 1997, Can. Res. 57:4414-4419). These results suggest that EGCg may prevent cancer at the level of gene transcription, i.e., by blocking the DNA synthesis of genes involved in signal transduction pathways.
Further, the focus of many other studies has been the effect of EGCg on apoptosis, or programmed cell death. Apoptosis differs from necrosis, and is regarded as an ideal mechanism for the elimination of cells. Studies have shown that several anti-cancer preventative agents may induce apoptosis, and conversely, several tumor-promoting agents inhibit apoptosis (Wright et al., 1994, FASEB J 8:654-660 and Ahmad and Mukhtar, 1999, Nutr. Rev. 57:78-83).
Much of the prior work in the art has attempted to determine what, if any, effect EGCg has on the growth inhibition and apoptosis induction of cancer cells. A differential growth inhibitory effect was reported in human colorectal cancer cells CaCo-2, breast cancer cells Hs578T, and their non-cancer cell counterparts (Ahmad and Mukhtar, 1999, Nutr. Rev. 57:78-83). EGCg has been implicated in the growth arrest and subsequent induction of apoptosis following cell growth inhibition has been shown in virally transformed fibroblast cells WI138, human epidermal carcinoma cells A431, lung cancer tumor cells H611, prostate cancer cell lines LNCaP, PC-3, and DU145, human carcinoma keratinocytes HaCaT, and mouse lymphoma cells LY-R (Chen et al., 1998, Can. Lett. 129:173-179; Ahmad et al., 1997, J. of the Nat. Can. Inst. 89:1881-1886; Yang et al., 1998, Carcinogenesis 19:611-616; Paschka et al., 1998, Can. Lett. 130:1-7; and Ahmad and Mukhtar, 1999, Nutr. Rev. 57:78-83). In studies where the apoptotic response was studied in cancer cells versus their non-cancer counterparts, e.g., human carcinoma keratinocytes HaCaT versus normal human epidermal keratinocytes, the apoptotic response to EGCg was reported to be specific to the cancer cells (Ahmad et al., 1997, J. Nat. Can. Inst. 89:1881-1886).
It has been suggested that EGCg induced apoptosis may result from either cell cycle arrest and/or H2O2 production (Ahmad et al., 1997, J. Nat. Can. Inst. 89:1881-1886; Fujiki et al., 1998, Mutat. Res. 402:307-310; and Yang et al., 1998, Carcinogenesis 19:611-616). EGCg may be involved in the growth regulation of human epidermal carcinoma cells A431 by causing cell cycle arrest of the G0 to G1 phase (Ahmad et al., 1997, J. Nat. Can. Inst. 89:1881-1886). EGCg has also been implicated in phase arrest between G2 to M phase of the cell cycle in human lung cancer cells (Fujiki et al., 1998, Mutat. Res. 402:307-310). In the EGCg induced inhibition of human lung cancer cells, it was suggested that the tumor necrosis factor (TNF) xcex1 pathway that is the mode of action of EGCg. Alternatively, the EGCg-induced apoptosis of the lung cancer tumor cells H611 is inhibited by catalase, suggesting the H2O2 production as a probable cause of apoptosis (Yang et al., 1998, Carcinogenesis 19:611-616).
Despite the above studies, the efficacy of EGCg as a single agent therapy for the prevention of cancer is still unclear. Moreover, the efficacy of EGCg as a therapeutic drug to treat or reverse cancer in a patient is unknown.
Although the focus of much of the prior research has been on EGCg, the putative biological functions of some of the other catechins has been examined. For example, both epicatechin gallate (ECG) and epigallocatechin (EGC) have been reported to be as effective as EGCg in inducing apoptosis of human epidermal carcinoma cells A431 at similar concentrations, whereas epicatechin (EC) did not show a similar effect (Ahmad et al., 1997, J. of the Nat. Can. Inst. 89:1881-1886). Growth inhibition in lung tumor cell lines H661 and H1299 was also observed with EGCg and EGC, whereas ECG and EC were less effective (Yang et al., 1998, Carcinogenesis 19:611-616).
Catechins have been implicated in growth inhibition of the human lung cancer cell line PC-9, with the order of catechin potency being reported as EGCg=ECG greater than EGC greater than  greater than  greater than EC (Okabe et al., 1993, Jpn. J. Clin. Oncol. 23:186-190). It has also been demonstrated that catechin combinations of EGCg and EC, ECG and EC, and EGC and EC induce apoptosis of the human lung cancer cell line PC-9 in vitro (Suganuma et al., 1999, Can. Res. 59:44-47). EC is thought to enhance incorporation of EGCg into the cells, which is thought to inhibit TNF xcex1 release resulting in the induction of apoptosis (Suganuma et al., 1999, Can. Res. 59:44-47).
Green tea extract has previously been reported to enhance the effect of the anti-cancer agents, e.g., adriamycin and doxorubicin (Sugiyama and Sadzuka, 1998, Can. Lett. 133:19-26 and Sadzuka et al., 1998, Clin. Can. Res. 4:153-156). Green tea in combination with adriamycin inhibits tumor growth in M5076 ovarian sarcoma cells, whereas adriamycin alone does not inhibit tumor growth in M5076 ovarian sarcoma cells (Sugiyama and Sadzuka, 1998, Can. Lett. 133:19-26). A similar effect is observed with green tea extract and doxorubicin on the same M5076 ovarian sarcoma cell line. Green tea extract, in combination with doxorubicin, also enhances the inhibitory growth effect on Ehrlich ascites carcinoma tumors in tumor-bearing mice, presumably by increasing the concentration of doxorubicin concentration in the tumor, but not in normal tissue (Sadzuka et al., 1998, Clin. Can. Res. 4:153-156).
EGCg has also been shown to enhance the effect of cancer prevention drugs in vitro. For example, EGCg has been shown to enhance the apoptotic effect of sulindac and tamoxifin, presumably by EGCg enhancing the intracellular concentration of the cancer prevention drugs. (Suganuma et al., 1999, Can. Res. 59:44-47). Both sulindac and tamoxifin induce apoptosis of human cancer cells and inhibit TNF xcex1 release from BALB/c-3T3 cells (Piazza et al., 1995, Can. Res. 55:3110-3116; Chen et al., 1996, J. Cell. Biochem. 61:9-17; and Sugunama et al., 1996, Can. Res. 56:3711-3715).
A unique plasma membrane NADH oxidase (NOX), a unique cell surface protein with hydroquinone (NADH) oxidase and protein disulfide-thiol interchange activities that is responsive to hormone and growth factors has been identified (Brightman et al., 1992, Biochim. Biophys. Acta 1105:109-117; Morrxc3xa9, 1994, J. Bioenerg. Biomemb. 26:421-433; and Morrxc3xa9, 1998, Plasma Membrane Redox Systems and their Role in Biological Stress and Disease, Klewer Academic Publishers, Dordrecht, The Netherlands, pp. 121-156). Further, a hormone-insensitive and drug-responsive form of NOX designated tNOX which is specific to cancer cells has been reported (Bruno et al., 1992, Biochem. J. 284:625-628; Morrxc3xa9 and Morrxc3xa9, 1995, Protoplasma 184:188-195; Morrxc3xa9 et al., 1995, Proc. Natl. Acad. Sci. U.S.A. 92;1831-1835; Morrxc3xa9 et al., 1995, Biochim. Biophys. Acta 1240:11-17; Morrxc3xa9 et al., 1996, Eur. J. Can. 32A: 1995-2003; and Morrxc3xa9 et al., 1997, J. Biomemb. Bioenerg. 29:269-280).
Because the NOX protein is located at the external plasma membrane surface and is not transmembrane, a functional role as an NADH oxidase is not considered likely (Morrxc3xa9, 1994, J. Bioenerg. Biomemb. 26:421-433; DeHahn et al., 1997, Biochim. Biophys. Acta 1328:99-108; and Morrxc3xa9, 1998, Plasma Membrane Redox Systems and Their Role in Biological Stress and Disease, Klewer Academic Publishers, Dordrecht, The Netherlands, pp. 121-156). While the oxidation of NADH provides a basis for a convenient method to assay the activity, the ultimate electron physiological donor is most probably hydroquinones with specific activities for hydroquinone oxidation greater than or equal to that of NADH oxidation and/or protein thiol-disulfide interchange (Kishi et al., 1999, Biochim. Biophys. Acta 1412:66-77).
CNOX was originally defined as a drug-indifferent constitutive NADH oxidase activity associated with the plasma membrane of non-transformed cells that was the normal counterpart to tNOX (Morrxc3xa9, 1998, Plasma Membrane Redox Systems and Their Role in Biological Stress and Disease, Kiewer Academic Publishers, Dordrecht, The Netherlands, pp. 121-156). Indeed, a 36 kD protein isolated from rat liver and from plants has NOX activity that is unresponsive to tNOX inhibitors (Brightman et al., 1992, Biochim. Biophys. Acta 1105: 109-117).
While cancer cells exhibit both drug-responsive and hormone and growth factor-indifferent (tNOX) as well as drug inhibited and hormone and growth factor dependent (CNOX) activities, non-transformed cells exhibit only the drug indifferent hormone- and drug-responsive CNOX. Among the first descriptions of so-called constitutive or CNOX activity of non-transformed cells and tissues was where the activity of rat liver plasma membranes was stimulated by the growth factor, diferric transferrin (Sun et al., 1987, J. Biol. Chem. 262:15915-15921). Subsequent work demonstrated that the observed NADH oxidation was catalyzed by a unique enzyme exhibiting responsiveness to several hormones and growth factors (Bruno et al., 1992, Biochem J. 284:625-628). Unlike mitochondrial oxidases, the hormone-stimulated NADH oxidase activity of rat liver plasma membranes is not inhibited by cyanide (Morrxc3xa9, 1994, J. Bioenerg. Biomemb. 26: 421-433). The enzyme also was distinguished from other oxidase activities by its response to several common oxidoreductase inhibitors, e.g., catalase, azide and chloroquine, as well as to various detergents e.g., sodium cholate, Triton X-100 and CHAPS (Morrxc3xa9 and Brightman, 1991, J. Bioenerg. Biomemb. 23:469-489 and Morrxc3xa9 et al., 1997, J. Biomemb. Bioenerg. 29:269-280). Like tNOX of cancer cells, CNOX is a unique membrane-associated protein that is capable of oxidizing NADH but has an activity which is modulated by hormones and growth factors.
Cancer is characterized primarily by an increase in the number of abnormal cells derived from a given normal tissue, invasion of adjacent tissues by these abnormal cells, and lymphatic or blood-borne spread of malignant cells to regional lymph nodes and to distant sites (metastasis). Clinical data and molecular biologic studies indicate that cancer is a multistep process that begins with minor preneoplastic changes, which may under certain conditions progress to neoplasia.
Pre-malignant abnormal cell growth is exemplified by hyperplasia, metaplasia, or most particularly, dysplasia (for review of such abnormal growth conditions, see Robbins and Angell, 1976, Basic Pathology, 2d Ed., W. B. Saunders Co., Philadelphia, pp. 68-79) Hyperplasia is a form of controlled cell proliferation involving an increase in cell number in a tissue or organ, but without significant alteration in structure or function. As but one example, endometrial hyperplasia often precedes endometrial cancer. Metaplasia is a form of controlled cell growth in which one type of adult or fully differentiated cell substitutes for another type of adult cell. Metaplasia can occur in epithelial or connective tissue cells. A typical metaplasia involves a somewhat disorderly metaplastic epithelium. Dysplasia is frequently a forerunner of cancer, and is found mainly in the epithelia; it is the most disorderly form of non-neoplastic cell growth, involving a loss in individual cell uniformity and in the architectural orientation of cells. Dysplastic cells often have abnormally large, deeply stained nuclei, and exhibit pleomorphism. Dysplasia characteristically occurs where there exists chronic irritation or inflammation, and is often found in the cervix, respiratory passages, oral cavity, and gall bladder.
The neoplastic lesion may evolve clonally and develop an increasing capacity for invasion, growth, metastasis, and heterogeneity, especially under conditions in which the neoplastic cells escape the host""s immune surveillance (Roitt, Brostoff, and Kale, 1993, Immunology, 3rd ed., Mosby, St. Louis, pp. 17.1-17.12).
There remains a need for treatment of cancer that does not have the adverse effects generally caused by non-selectivity, of conventional chemotherapeutic agents. None of the above studies, which are not to be construed as an admission that any of the above studies is prior art, have suggested the present mechanism by which the catechins are able to differentiate between cancer and non-cancer cells. Moreover, none of the studies evaluated the efficacy of varying levels of catechin combinations or compositions of multiple catechins for the treatment of cancer. In contrast, the Inventors have identified a cancer-specific isoform of a unique plasma membrane NADH oxidase (tNOX) which is inhibited by the catechins. Furthermore, the studies cited supra have hypothesized that EGCg mediates its effects intracellularly, since EGCg incorporation into the cell seems to be a prerequisite for the inhibition of TNF xcex1 release. Inhibition of tNOX, an extracellular membrane-associated protein) by EGCg, and synergistically with other catechins and anti-cancer agents, results in the selective inhibition of cancer cell growth and ultimately, apoptosis. Further discussion of catechin-induced apoptosis wherein tNOX is targeted is presented in Sections 6, 7, and 8.
The invention described herein encompasses a method of treating cancer or solid tumors comprising the administration of a therapeutically effective amount of catechins, a group of polyphenols found in green tea, to a mammal in need of such therapy. In a preferred embodiment, the mammal is a human. In another embodiment, the invention further encompasses the use of combination therapy to treat cancer.
In a specific embodiment, the catechins comprise epigallocatechin gallate (EGCg), epicatechin gallate (ECG), epigallocatechin (EGC), and epicatechin (EC) or a combination thereof, optionally in combination with other polyphenols or other anti-cancer therapeutic agents.
The disclosure is based, in part, on the discovery that epigallocatechin gallate (EGCg), alone and in combination with other catechins and other anti-cancer therapeutic agents, inhibits the activity of a cancer-specific protein, an isoform of NADH oxidase specific to cancer cells (tNOX). The inhibition of tNOX results in the inhibition of cell growth, and ultimately, apoptosis of the cancer cell, whereas normal cells (which lack tNOX but instead express the isoform CNOX) are less affected. Thus, the invention provides a potent therapeutic effect without or while reducing the adverse effects on normal, healthy cells.
The invention is also based, in part, on the discovery that the effect of EGCg is reversible, i.e., if the EGCg is removed, cancer cells resume normal rates of growth. Other discoveries include: (1) EGCg is rapidly cleared from the blood and metabolized, (2) cancer cells must be inhibited from growing for 48 to 72 hours before EGCg-induced apoptosis occurs, and (3) when cancer cells are challenged with 10xe2x88x927 M EGCg every two hours during the day, their growth is inhibited, but during the night normal cell growth resumes in the absence of further EGCg addition. Thus, the invention includes a unique feature of administration comprising a sustained release formulation so a constant level of EGCg is maintained.
In accordance with the present invention, the catechins can be used alone or in combination with other known therapeutic agents or techniques to either improve the quality of life of the patient, or to treat cancer or solid tumors. The catechins can be used before, during, or after the administration of one or more known chemotherapeutic agents, including antitumor agents. In addition, the catechins can be used before, during, or after radiation treatment.
In another embodiment, the compositions of the invention are sterile pharmaceutical compositions suitable for intravenous injection or infusion. In another embodiment, the invention encompasses a composition suitable for oral delivery, comprising catechins and a pharmaceutically acceptable excipient or carrier. A preferred embodiment comprises a sustained release composition to maintain the circulating levels of said composition at a certain minimum level for therapeutic efficacy over a specified time period. Specific therapeutic regimens, pharmaceutical compositions, and kits are also provided by the invention.
Particular compositions of the invention and their uses are described in the sections and subsections which follow.
As used herein, the term xe2x80x9ccancerxe2x80x9d describes a diseased state in which a carcinogenic agent or agents causes the transformation of a normal cell into an abnormal cell, the invasion of adjacent tissues by these abnormal cells, and lymphatic or blood-borne spread of malignant cells to regional lymph nodes and to distant sites, i.e., metastasis.
As used herein, the terms xe2x80x9ctreating cancerxe2x80x9d and xe2x80x9ctreatment of cancerxe2x80x9d mean to inhibit the replication of cancer cells, to inhibit the spread of cancer, to decrease tumor size, to lessen or reduce the number of cancerous cells in the body, and to ameliorate or alleviate the symptoms of the disease caused by the cancer. The treatment is considered therapeutic if there is a decrease in mortality and/or morbidity.
The term xe2x80x9csynergisticxe2x80x9d as used herein refers to a combination which is more effective than the additive effects of any two or more single agents. A determination of a synergistic interaction between catechins, and another therapeutic agent may be based on the results obtained from the NOX assays described in Section 5.4 infra. The results of these assays are analyzed using Chou and Talalay""s combination method and Dose-Effect Analysis with Microcomputers"" software in order to obtain a Combination Index (Chou and Talalay, 1984, Adv. Enzyme Regul. 22:27-55 and Chou and Chou, 1987, software and manual, Elsevier Biosoft, Cambridge, UK, pp. 19-64). Combination Index values less than 1 indicates synergy, values greater than 1 indicate antagonism and values equal to 1 indicate additive effects.
The term xe2x80x9cpharmaceutically acceptable carrierxe2x80x9d refers to a carrier medium that does not interfere with the effectiveness of the biological activity of the active ingredient, is chemically inert and is not toxic to the patient to whom it is administered.
The term xe2x80x9cpharmaceutically acceptable saltsxe2x80x9d refers to salts prepared from pharmaceutically acceptable non-toxic acids and bases, including inorganic and organic acids and bases.
As used herein the term xe2x80x9cpharmaceutically acceptable derivativexe2x80x9d refers to any homolog, analog, or fragment corresponding to the catechin formulations as described in Section 5.1 infra which exhibits anti-cancer activity and is relatively non-toxic to the subject.
The term xe2x80x9ctherapeutic agentxe2x80x9d refers to any molecule, compound or treatment that assists in the treatment of a cancer or the diseases caused thereby.
The catechins and target proteins defined herein are abbreviated as follows: